Startup puts wireless monitor on a band-aid

SAN FRANCISCO, Calif.  Sometime next year nurses may put active band-aids on hospital patients to wirelessly monitor as many as three vital signs. Startup Toumaz Technology (Abingdon, U.K.) described its custom chip to power such a disposable device at the International Solid State Circuits Conference here Monday (Feb. 4).

The chip is one of an emerging group of smart wearable devices that ultimately aim to help patients get medical monitoring from the comfort of home.

"We not only have an aging society, but one that does not have healthy lifestyle," said Alison Burdett, director of technology for Toumaz. "There are increasing numbers of people with chronic ailments, and that's putting an enormous burden on health care systems worldwide," she added.

A large U.S. health care company is said to be working with Toumaz, aiming to field the silicon-backed band-aids in a hospital setting before the end of 2009. Other giants include GE and Philips are said to have similar projects in the lab.

The chip aims to have a 5-7 day life based on a printed zinc battery that measures about 10 cm-squared.

To keep power down and reliability up, Toumaz developed custom hardware and protocols for the 800-900 MHzwireless network the devices use at data rates up to 50 Kbits/second. The chip draws 2.5 milliA when communicating, but its digital control portion dissipates just 100 microW.

"A custom media access controller is crucial because in short range communications there is always interference, and we have many layers of mitigation," Burdett said.

Despite the custom design, the active patch is expected to cost as little as $5 when it hits the market next year. The 16 mm-squared chip made in an 130nm process by Infineon will be a small fraction of that cost.

"When this is in volume production the silicon doesn't rally cost anything," said Burdett. "The big cost is in the assembly and manufacturing because this requires new processes," she added.

The chip can interface to sensors for an electrocardiogram, a three-axis accelerometer, as well as blood glucose, ph-level and pressure monitors. It can only measure from one sensor at a time but does have a capability to switch between three sensors.

Just how the chip will be used in practice has yet to be fully determined. This the first generation part builds in a programmability into its sensor interfaces, network controller and an 8051 processor core. "Once we get this out there, we will get a better idea of what people want to do with it," said Burdett.

Currently Toumaz is shipping sample quantities of its chip. It is being used in non-disposable applications in a "pebble-like" package to monitor performance of athletes on the field and handle continuous monitoring in clinical field trials for new drugs. The chip will be in production in August.